Problems rendering hair in cycles render
Whenever it comes to differences with particle systems between preview and final render it almost always has something to do with the subsurf modifier. 


Always make sure that you have the subsurf modifier enabled in Render and Preview mode when you use "Particle Edit" (cut, comb, etc.). I believe that you had it turned on, when you combed the hair, since it is activated in your file (see image below)
Always set the viewport and render settings to the same value when rendering particle systems. If the render setting is lower than the viewport setting (which is the case in your file, see image below) the render process will undo or at least mess up your combed hair. 




Try to set the viewport subdivs to 2 and you'll get the same messed up hair effect you had after rendering. 

Set the Render subdivs to 3 and your problem should be gone.